In recent years, there have been developed techniques for inserting a metallic wire or a metallic part into an in-mold foaming molded body for use in vehicles and molding them simultaneously. As an example of component into which a metallic wire is inserted, there is a seat core material for vehicles, for example. The seat core material has as a foam a polyolefin-based resin foaming molded body higher in strength than urethane to provide the advantage of reducing significantly the amount of the metallic wire that has been used to hold the shape of the seat, thereby resulting in weight saving. As another case, there has been proposed a technique for inserting a metallic part to be attached to a vehicle beam into a vehicle bumper core material formed from a foaming molded body and molding them integrally to fix the bumper core material more firmly to the vehicle. In addition, as still another case, there has been proposed a technique for molding a metallic part integrally with a headrest formed from a foaming molded body to not only produce the stronger and safer component but also decrease the number of components, thereby advantageously improving workability and achieving cost cutting.
However, in order to fix the foaming molded article to the vehicle, the foaming molded article needs to have metallic fastening members composed of U- or V-shaped hooks and protruding toward the outside. However, this leads to the occurrence of large burrs around the protrusion parts of the fastening members protruding from the foaming molded article, in particular, inside the protrusion parts composed of hooks. The burrs have to be trimmed off after the molding, which causes significant decrease in productivity.
Meanwhile, various methods have been used to prevent the occurrence of burrs in a foaming molded body. For example, Patent Document 1 discloses an invention of urethane molding in which a gasket is applied to the juncture of mold such that the gasket protrudes toward the inside of the mold at the time of mold clamping to prevent overflow of a urethane resin from a parting surface. In addition, Patent Document 2 discloses an invention of a method for preventing the occurrence of burrs on a parting surface in in-mold foam molding by which the parting surface of the mold is formed in a concave shape such that burrs fall within the concave part of the molded product. Further, Patent Document 3 discloses a technique for preventing the occurrence of burrs on places other than the parting surface by which the partitioning part of the mold with a partitioning plate for simultaneously molding preparatory foaming particles with different properties is protruded toward the product side such that burrs fall within a groove in the product. However, none of the inventions disclosed in Patent Documents 1 to 3 are applicable as a method for preventing the occurrence of burrs around the fastening members.